1. Field of the Invention
The present invention relates to an image sensor for use in a facsimile machine, an image scanner, or the like.
2. Description of the Prior Art
An image sensor generally includes an array of light receiving elements, for example photosensors, for dividing an image into fine pixels and reads image information by scanning such an array along the image plane. To accurately read the image information, a light emitting mechanism is required which emits a sufficient amount of light to the image plane. The light emitting mechanism provided in conventional image sensors generally includes an array of light emitting elements, for example LEDs (light emitting diodes), along with an array of light receiving elements. In this mechanism, lights emitted from the light emitting elements are initially reflected by the image plane and then inputted into the light receiving elements.
FIG. 1 depicts the structure of a conventional image sensor having an array of photosensors 1 mounted on a circuit board 2. The light receiving surface of each photosensor 1 confronts one end of a light wave guide 3, which comprises a core 3a for guiding light and a cladding 3b covering the core 3a. The light wave guides 3 are placed substantially vertically and the other ends thereof are disposed in close proximity to the image plane of an original document 4. The light wave guides 3 are mounted on a base 6 of the image sensor.
An array of LEDs 5 is mounted on a separate circuit board 5a from the circuit board 2 and placed beside the light wave guides 3. The LEDs 5 are orientated obliquely downwards towards the other ends of respective light wave guides 3 so as to effectively emit lights to the image plane of the document 4 placed immediately below them. The lights reflected by the image plane are then properly inputted into the light wave guides 3. To obliquely place the LEDs 5, the LEDs 5 and the circuit board 5a are mounted on an inclined surface of the base 6. The circuit board 2, on which the photosensors 1 are mounted, is mounted on the upper surface of the base 6 by means of screws 2a or any other suitable means. A cover 6a is attached to the base 6 to cover the photosensors 1 and the circuit board 2.
The above-described conventional image sensor inevitably requires two kinds of circuit boards 2 and 5a, on which the LEDs 5 and the photosensors 1 are separately mounted and which must be placed apart from each other. Accordingly, the cost of parts becomes high, and the manufacturing process of the image sensor, for example the assembling of the circuit boards 2 and 5a, electric wiring therefor, or the like, takes a lot of labor.